CN1148961C - Method for embedding digital watermark - Google Patents

Method for embedding digital watermark Download PDF

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CN1148961C
CN1148961C CNB021151741A CN02115174A CN1148961C CN 1148961 C CN1148961 C CN 1148961C CN B021151741 A CNB021151741 A CN B021151741A CN 02115174 A CN02115174 A CN 02115174A CN 1148961 C CN1148961 C CN 1148961C
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watermark
wavelet
image
coefficient
embedding
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CN1377184A (en
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刘九芬
黄达人
黄继武
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Sun Yat Sen University
National Sun Yat Sen University
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T1/00—General purpose image data processing
    • G06T1/0021—Image watermarking
    • G06T1/0028—Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2201/00—General purpose image data processing
    • G06T2201/005—Image watermarking
    • G06T2201/0052—Embedding of the watermark in the frequency domain

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Abstract

The present invention relates to a digital watermark technology based on wavelet transformation, particularly to a multimedia video data protection method which belongs to the field of multimedia signal processing. The present invention comprises the following steps that firstly, the stage number of wavelet decomposition is selected and multimedia data is decomposed by means of the wavelet transformation; then, a great number of wavelet coefficients are selected and are embedded into a watermark according to definite rules; multimedia data for embedding the watermark is obtained through inverse wavelet transformation. Compared with original media, human eyes or ears can not distinguish the differences of both and a digital watermark provides a distinguishable means for the problem. The watermark can be any meaningful digital file or meaningless random sequence and the present invention can protect the multimedia data or files through network propagation.

Description

A kind of embedding grammar of digital watermarking
Technical field:
The present invention relates to a kind of digital watermark technology based on wavelet transformation, is a kind of multimedia data protection method, belongs to field of multimedia signal processing.
Technical background:
There is the incomparable advantage of some analog medias in Digital Media, as digital signal high-quality, edit and process easily, copy is undistorted, be easy to (CD-ROM) system transmission and the distribution etc. rapidly efficiently at a low price by (network) or the physics of electronics.These advantages make Digital Media recent years (digital audio, digital image, digital video) technological development and use fast development.Yet also just because of these advantages, caused potential threat for the original owner's of medium rights and interests: the every nook and cranny in the world might be duplicated and spread all over to the achievement of its hard working overnight by large quantities of perfections gratis.Thereby the copyright protection of Digital Media becomes a problem that presses for solution.Digital watermarking is then for solving an effective way of Digital Media Copyright Protection.In recent years, digital watermark technology had embodied its importance in many applications, and had obtained paying attention to widely.
The research and the document of present most of data hiddens concentrate on image watermark.According to the mode that watermark embeds, the digital watermark technology that proposes mainly can be divided into two classes at present: spatial domain and transform domain technology.The former comes watermarked by direct some pixel value of change main picture.The latter realizes in transform domain, earlier image is done certain conversion, then watermark is embedded in the transform domain of image.Because the good space-frequency local characteristics and the transformation mechanism that conforms to human-eye visual characteristic of DWT (Discrete Wavelet Transform), occupy core position in still image compression standard JPEG 2000 of new generation, and replaced DCT to become the main tool of transform domain digital watermarking algorithm gradually.
Famous and what accepted extensively by people is people's such as Cox viewpoint, the watermark of DCT territory should embed before the amplitude maximum in k the AC coefficient.Huangs etc. have further been promoted this thought, and it is watermarked to have proposed to utilize the DC component.But in the DWT territory, the research of this respect does not appear in the newspapers as yet, and the research of the progression of embedding formula and wavelet decomposition also still belongs to blank.
Summary of the invention:
The objective of the invention is to propose a kind of data waterprint embedded method, be used to improve the robustness of watermark, protection Digital Media copyright based on wavelet transformation.
To achieve these goals, the inventive method adopts following three steps:
1) what of the watermarked data volume of want to improve the progression of wavelet decomposition according to as far as possible, determine decomposed class after, initial data is carried out wavelet decomposition; 2) embedding formula is: ν i'=ν i+ α i, wherein, ν iBe wavelet coefficient, α is a stretching factor, x iIt is the watermark component; 3) at first embed the low-frequency band of wavelet coefficient by the embedding formula watermark, if residue is arranged, the clooating sequence of pressing wavelet coefficient frequency band importance again embeds high frequency band.
Step 1) is determined the progression of wavelet decomposition according to what of watermark data amount, and the progression of the wavelet decomposition height of will trying one's best carries out wavelet decomposition then.Embedding formula ν i'+ν i+ α x iIn stretching factor α guaranteeing under the sightless prerequisite of watermark, big as far as possible.
The clooating sequence of wavelet coefficient frequency band importance:
Select separable bank of filters, input imagery is carried out wavelet decomposition, produce LH j, HL j, HH jThree high frequency band series, a LL 3Low-frequency band (during three grades of decomposition) (as shown in Figure 1).Wherein low-frequency band is represented by under the out to out of wavelet transformation decomposed class decision, the minimum resolution the best of original picture being approached.Its statistical nature and former image similarity, most of concentration of energy of image is at this.High frequency band series then is respectively the detailed information of image under different scale, different resolution.Resolution is low more, and wherein the ratio of useful information is high more.That is to say, an image has been divided into some levels through wavelet decomposition.For with the one-level image, low frequency subgraph resembles LL jMost important, secondly be HL jWith LH j, high frequency image subsection HH jRelatively least important.For not at the same level, high person is important for level, and low person is inessential for level.So small echo image sub-band is LL by the overall ordering of its importance k, HL k, LH k, HH k, HL K-1, LH K-1, HH K-1..., HL 1, LH 1, HH 1(as shown in Figure 1).
The present invention and existing digital watermark relatively have following advantage:
By the embedding grammar (progression that comprises embedding formula, embedded location and wavelet decomposition) in research DWT territory and the relation of robustness, found reasonable embedding grammar.Compare with existing digital watermark, this technology has significantly improved the robustness of watermark.
Below we illustrate the good effect that the present invention brings from theoretical and experimental data.
1) progression of wavelet decomposition
Mallat proposed multiresolution analysis (MRA) in 1988, and it is the effective tool of signal analysis and processing.On the basis of MRA, S.Mallat has proposed to realize with sub band structure the algorithm of DWT, the calculating of having unified sub-filter and wavelet transformation.
Provide square can with 2D signal { x M, n} N1, n ∈ Z, order
c 0, m, n=x M, n, m, n ∈ Z then the wavelet decomposition formula of 2D signal are:
C j , m , n = 2 Σ k , l h l - 2 m h l - 2 n c j - 1 , k , l , d j , m , n 1 = 2 Σ k , l h k - 2 m g l - 2 n c j - 1 , k , l ,
d j , m , n 2 = 2 Σ k , l g k - 2 m h l - 2 n c j - 1 , k , l , d j , m , n 3 = 2 Σ k , l g k - 2 m g l - 2 n c j - 1 , k , l .
Wherein Σ k h k = 1 , g k＝(-1) nh 1-n， Σ k g k = 0 .
From top formula as can be known, wavelet decomposition be every grade with 2 weightings, and notices low-pass filter coefficients and be 1, thereby along with the increase of wavelet decomposition progression, the amplitude of low frequency coefficient increases with approximate 2 multiple.And watermark encoder can be seen as in strong background (original picture) weak signal of superposition (watermark) down, as long as the signal of superposition is lower than the contrast thresholding, vision system just can't be felt the existence of signal.And according to the Weber law, the amplitude of contrast thresholding and background signal is proportional.This just means the increase along with wavelet decomposition progression, and watermarked intensity increases considerably, thereby the robustness of watermark strengthens.Simultaneously, the progression of wavelet decomposition is many more, and the watermark component can spread better.Therefore in watermarking algorithm, should improve the progression of wavelet decomposition as far as possible according to what of watermark data amount.
2) embedded location
When the angle of multiresolution analysis is considered each frequency band of little wave image, be not pure irrelevant between these frequency bands.For each high frequency band, because they are the descriptions from coarse to fine under different directions, different scale and different resolution of visual same edge, profile and texture information, existing certain amplitude that concerns wavelet coefficient between them decays along with reducing of yardstick, even picture function has singular point, as long as vibration is not fierce in unusual neighborhood of a point.(x is y) at (x as if picture function f o, y o) to have Lipschitz α in the neighborhood continuous, then yardstick is 2 j, be positioned at (p, the amplitude of wavelet coefficient q) has: | α j(p, q) |≤A2 J (a+1)
Wherein A is a positive constant.Therefore the amplitude of wavelet coefficient decays along with reducing of yardstick.Mode does not have this character, and mode seldom runs in actual image luckily.Coding based on zero tree has utilized the amplitude of wavelet coefficient to decay this character along with reducing of yardstick and obtained howling success just.
Random sequence, significant text, image etc. can be as watermarks.The data volume difference that dissimilar watermarks comprises.The watermark of different pieces of information amount should have different embedding countermeasures.
Should where just enough sane watermark be placed on? in the DWT territory, different wavelet coefficients are as watermark carrier, and watermark has different robustnesss.
Watermark length is shorter:
Where should watermark embed when watermark length was not more than small echo image low frequency coefficient number?
At first, proposition such as Cox: watermark should be placed on the sensuously most important component of HVS.This viewpoint is accepted extensively by people now.Sensuously important component is the main component of picture intelligence, carries more signal energy, has at image under the situation of certain distortion, still can keep main component.But Cox etc. foreclose the DC coefficient, and reason is that blocking artifact appears in the image of avoiding adding watermark.Because wavelet transformation is a global change, the watermark image that watermark is added in low frequency coefficient blocking artifact can not occur.Simultaneously by the front as can be known: low-frequency band is that the low pass of original picture is approached, and most of concentration of energy of image is at this, and the just visual detailed information of high frequency band series.Therefore watermark should at first embed small echo image low frequency coefficient.
Secondly,,, thereby have bigger sensation capacity, embed the obvious change that can not cause the original picture visual quality after the watermark of certain intensity because the amplitude of low frequency coefficient is generally much larger than high frequency coefficient with the identical reason of the first step.
Once more, according to signal processing theory, the signal processing that watermarked image most possibly suffers from is as data compression, low-pass filtering, inferior sampling, interpolation, D/A and A/D conversion etc., good to the protective ratio high frequency coefficient of low frequency coefficient.Be that these wavelet coefficients still can keep after through common signal processing and noise jamming well, changed by signal processing and noise jamming with exceeding.
Therefore, the watermark component is embedded into DWT territory low frequency coefficient and has enough robustnesss.
Watermark length is longer:
When watermark length during,, at first utilize HL except watermark is embedded the low-frequency band coefficient greater than small echo image low frequency coefficient number 3The coefficient of (three grades of decomposition) band comes watermarked.This be because: 1) HL 3Band is most important in high frequency band series.2) HL 3The coefficient of band is usually than the coefficient of other yardstick big (seeing this part beginning).In like manner, next should utilize LH 3The coefficient of band.By that analogy, we obtain as drawing a conclusion: when watermark length is longer, press the watermarked robustness of clooating sequence best (Fig. 1) of small echo image frequency band importance.
In sum, we carry out qualitative, quantitative analysis by characteristic distributions and the amplitude to small echo image coefficient, obtained a new embedding countermeasure: watermark should at first embed small echo image low frequency coefficient, if residue is arranged, the clooating sequence of pressing small echo image frequency band importance again embeds high frequency band.
3) embedding formula
Embedding formula also influences the robustness of watermark.Larynx commonly used is at present gone into formula two: (1) ν i'=ν i+ α x i(2) ν i'=ν i(1+ α x i), wherein α is a stretching factor.
Because embedding formula (1) is to the identical intensity of each wavelet coefficient stack, watermark image under fire after, watermark component possibility portion exists with certain intensity.But concerning embedding formula (2) because the big intensity of big coefficient stack, the little little intensity of coefficient stack, watermark image under fire after, the watermark component of little coefficient may not exist.Only under the very strong situation of attack strength, do not existed based on the watermark component of embedding formula (1), still exist based on the watermark component of the big coefficient of embedding formula (2).But this situation seldom exists.
Therefore, embedding formula (1) is reasonable selection.
We with the image " Lena " of the fairly simple and more complicated of texture (256 * 256 * 8bits) and " Baboon " (256 * 256 * 8bits) are the test image.Experimental data shows that new method is very sane.
Description of drawings:
Fig. 1 is visual wavelet decomposition figure.
Fig. 2 be watermark can not the property comparison diagram.
Fig. 3 is the sane performance comparison diagrams of two kinds of identical situation watermark images of conditionally complete under JPEG compression and Gaussian noise jamming.
Embodiment:
Among Fig. 1, input imagery is carried out wavelet decomposition, produce LH j, HL j, HH jThree high frequency band series, a LL 3Low-frequency band (during three grades of decomposition).
Among Fig. 2, (a) for utilizing LL 3Watermarked watermark image; (b) for utilizing HL 3Watermarked watermark image.Under identical condition, when PSNR was 44.4dB, " Lena " first kind of situation watermark was invisible, and second kind of situation watermark obviously as seen, illustrates that low frequency coefficient has bigger sensation capacity.
Among Fig. 3, be that anti-JPEG compression performance compares (a); (b) be that anti-Gaussian noiseproof feature compares.The longitudinal axis is represented the watermark W that extracts from the watermark image of distortion *Similarity with original watermark W.Fig. 3 shows: at the watermarked ratio of low-frequency band coefficient at HL 3The band coefficient is watermarked steadily and surely good.The experiment that watermark is embedded on other high-frequency sub-band also can obtain similar results.
Table 1 is the robustness based on embedding formula (1).In the table, (a) the anti-JPEG of Lena watermark image (one-level decomposition) (b) the anti-noise of Baboon watermark image (one-level decomposition) is (c)) (d) the anti-noise of Lena watermark image (three grades of decomposition) of the anti-JPEG of Baboon watermark image (three grades of decomposition).
Table 2 is the robustness based on embedding formula (2).In the table 2, (a) the anti-JPEG of Lena watermark image (one-level decomposition) (b) the anti-noise of Baboon watermark image (one-level decomposition) is (c)) (d) the anti-noise of Lena watermark image (three grades of decomposition) of the anti-JPEG of Baboon watermark image (three grades of decomposition).
Wavelet basis selects Daubechies small echo DbN (1≤N≤10) among the table 1-2, after the anti-JPEG of all Baboon represents that the Baboon watermark image is subjected to the JPEG compression attack, and when PSNR is respectively 20db, 20.9db, 21.8db, 22.4db, 22.9db, the watermark W of extraction *Similarity with original watermark W; After the anti-JPEG of all Lena represents that the Lena watermark image is subjected to the JPEG compression attack in the table, when PSNR is respectively 23.1db, 25db, 26.9db, 28.1db, 29db, the watermark W of extraction *Similarity with original watermark W.After the anti-noise of all Baboon represents that the Baboon watermark image is subjected to additivity Gaussian attacked by noise in the table, when PSNR is respectively 18.7db, 16.3db, 14.6db, 13.2db, 12.2db, the watermark W of extraction *Similarity with original watermark W; After the anti-noise of all Lena represents that the Lena watermark image is subjected to additivity Gaussian attacked by noise in the table, when PSNR is respectively 18.7db, 16.3db, 14.6db, 13.1db, 12.1db, the watermark W of extraction *Similarity with original watermark W.
Table 1: based on the robustness of embedding formula (1)
(a) (b)
Db1 ?2.82 ?5.13 ?7.34 ?8.54 ?10.76
Db2 ?2.78 ?5.08 ?7.09 ?8.1 ?10.03
D173 ?2.41 ?5.14 ?6.77 ?7.54 ?9.04
Db4 ?1.79 ?4.98 ?6.55 ?7.07 ?8.15
Db5 ?1.56 ?4.93 ?6?43 ?7.55 ?8.65
Db6 ?2.25 ?5.14 ?6.79 ?7.65 ?9.71
Db7 ?1.79 ?5.16 ?6.74 ?7.91 ?10.08
Db8 ?1.43 ?5.11 ?6.32 ?8.09 ?10.56
Db9 ?0.91 ?4.54 ?5.9 ?7.69 ?9.65
Db10 ?0.71 ?4.6 ?5.5 ?6.96 ?9.31
?Db1 ?14.90 ?11.36 ?9.12 ?7.64 ?6.53
?Db2 ?14.61 ?11.07 ?8.84 ?7.37 ?6.28
?Db3 ?14.54 ?10.99 ?8.78 ?7.30 ?6.22
?Db4 ?14.3 ?10.75 ?8.57 ?7.09 ?6.01
?Db5 ?13.91 ?10.37 ?8.21 ?6.75 ?5.66
?Db6 ?13.52 ?9.96 ?7.83 ?6.38 ?5.28
?Db7 ?13.11 ?9.54 ?7.42 ?5.99 ?4.89
?Db8 ?12.70 ?9.12 ?7.01 ?5.57 ?4.48
?Db9 ?12.31 ?8.72 ?6.60 ?5.16 ?4.08
?Db10 ?12.08 ?8.47 ?6.34 ?4.89 ?3.82
(c) (d)
?Db1 ?2.54 ?6.66 ?11.39 ?13.03 ?15.2
?Db2 ?4.01 ?6.86 ?11.67 ?14.76 ?15.96
?Db3 ?3.99 ?6.86 ?12.91 ?15.63 ?17.88
?Db4 ?4.88 ?6.88 ?12.02 ?15.62 ?18.06
?Db5 ?5.05 ?7.25 ?11.81 ?14.78 ?17.70
?Db6 ?4.75 ?5.86 ?11.46 ?14.64 ?18.21
?Db7 ?3.94 ?5.50 ?11.74 ?14.13 ?18.06
?Db8 ?3.71 ?5.27 ?11.87 ?14.13 ?17.96
?Db9 ?4.06 ?6.91 ?11.50 ?13.97 ?16.83
?Db10 ?3.86 ?6.92 ?11.28 ?13.60 ?16.66
?Db1 ?13.1 ?10.17 ?8.13 ?6.52 ?5.22
?Db2 ?13.03 ?10.0 ?7.86 ?6.19 ?4.84
?Db3 ?13.22 ?10.18 ?8.07 ?6.45 ?5.11
?Db4 ?13.74 ?10.8 ?8.75 ?7.16 ?5.85
?Db5 ?14.31 ?11.46 ?9.43 ?7.85 ?6.56
?Db6 ?13.83 ?10.97 ?8?96 ?7.45 ?6.25
?Db7 ?12.81 ?9.87 ?7.87 ?6.44 ?5.33
?Db8 ?12.07 ?9.08 ?7.1 ?5.7 ?4.65
?Db9 ?12.29 ?9.31 ?7.35 ?5.93 ?4.88
?Db10 ?13.12 ?10.23 ?8.3 ?6.86 ?5.79
Table 2: based on the robustness of embedding formula (2)
(a) (b)
?Db1 ?2.49 ?3.97 ?5.83 ?6.83 ?8.1
?Db2 ?2.52 ?3.82 ?5.46 ?6.45 ?7.46
?Db3 ?2.16 ?3.83 ?5.2 ?5.91 ?6.7
?Db4 ?1.49 ?3.84 ?4.89 ?5.87 ?6.07
?Db5 ?1.43 ?3.74 ?4.58 ?5.92 ?6.61
?Db6 ?1.25 ?3.73 ?4.71 ?5.97 ?7.05
?Db7 ?0.95 ?3.25 ?4.70 ?5.75 ?7.73
?Db8 ?0.62 ?3 ?4.08 ?5.42 ?7.24
?Db9 ?0.35 ?2.85 ?3.92 ?5.29 ?7.06
?Db10 ?0.01 ?2.93 ?3.79 ?4.93 ?6.52
?Db1 ?10.71 ?8.03 ?6.28 ?5.02 ?4.14
?Db2 ?10.40 ?779 ?6.11 ?4.87 ?4.03
?Db3 ?2.45 ?2.97 ?3.58 ?4.06 ?4.05
?Db4 ?10.04 ?7.31 ?5.53 ?4.3 ?3.44
?Db5 ?10.68 ?8.12 ?6.47 ?5.28 ?4.47
?Db6 ?2.89 ?2.17 ?1.68 ?1.34 ?1.09
?Db7 ?9.12 ?6.62 ?5.13 ?4.15 ?3.49
?Db8 ?8.86 ?6.23 ?4.55 ?3.42 ?2.63
?Db9 ?8.06 ?6.24 ?5.08 ?4.34 ?3.81
?Db10 ?5.26 ?3.58 ?2.54 ?1.83 ?1.39
(c) (d)
?Db1 ?2.17 ?5.88 ?9.47 ?11 ?12.35
?b2 ?2.54 ?5.78 ?10.14 ?12.04 ?13.85
?Db3 ?3.38 ?5.48 ?11.1 ?14.5 ?15.47
?Db4 ?3.69 ?5.93 ?10.36 ?13.73 ?15.94
?Db5 ?3.54 ?7.29 ?10.14 ?12.4 ?15.52
?Db6 ?3.90 ?6.22 ?9.53 ?12.52 ?15.28
?Db7 ?3.46 ?4.47 ?10.25 ?11.77 ?15.79
?Db8 ?2.32 ?4.14 ?10.06 ?12.43 ?15.70
?Db9 ?2.37 ?5.18 ?9.18 ?13.12 ?14.85
?Db10 ?3.04 ?5.16 ?9.75 ?12.39 ?14.27
?Db1 ?10.39 ?8.01 ?7.09 ?5.56 ?4.34
?Db2 ?11.48 ?8.74 ?6.75 ?5.16 ?3.9
?Db3 ?11.56 ?8.77 ?6.77 ?5.22 ?3.98
?Db4 ?12.09 ?9.37 ?7.4 ?5.86 ?4.63
?Db5 ?12.47 ?9.86 ?7.95 ?6.42 ?5.2
?Db6 ?11.77 ?9.17 ?7.30 ?5.86 ?4.71
?Db7 ?10.38 ?7.73 ?5.90 ?4.54 ?3.49
?Db8 ?9.48 ?6.79 ?4.96 ?3.63 ?2.64
?Db9 ?9.91 ?7.21 ?5.36 ?3.97 ?2.95
?Db10 ?10.96 ?8.35 ?6.50 ?5.07 ?3.98

Claims (1)

1, a kind of embedding grammar of digital watermarking is characterized in that: 1) initial data is carried out wavelet decomposition; 2) embedding formula is: ν i'=ν i+ α x i, wherein, ν iBe wavelet coefficient, α is a stretching factor, x iIt is the watermark component; 3) watermark at first embeds the low-frequency band of wavelet coefficient by embedding formula, if the watermark component also has residue, press the clooating sequence embedding high frequency band of wavelet coefficient frequency band importance again.
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CN100364260C (en) * 2004-01-18 2008-01-23 哈尔滨工业大学 Method for making and verifying digital signature and digital watermark bar code
CN100399353C (en) * 2006-07-07 2008-07-02 中山大学 Electronic stamp certification method based on image features
WO2014199449A1 (en) * 2013-06-11 2014-12-18 株式会社東芝 Digital-watermark embedding device, digital-watermark detection device, digital-watermark embedding method, digital-watermark detection method, digital-watermark embedding program, and digital-watermark detection program
CN103559677B (en) * 2013-10-29 2016-04-20 华北电力大学 Based on the adapting to image watermark embedding method of wavelet transformation and visual characteristic
CN105719226B (en) * 2016-01-26 2019-03-15 陕西师范大学 A kind of combination non-overlap piecemeal and the watermark insertion and extracting method for waiting frequency bands to merge
CN109146520A (en) * 2018-08-17 2019-01-04 珠海丹德图像技术有限公司 A kind of Comodity anti-fake system and method based on image information safe practice

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